Chair back



FIG. 1 is a top left front perspective view of a chair back showing our new design. The broken lines are for illustrative purposes only and form no part of the claimed design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a top plan bottom plan view thereof;

FIG. 4 is a rear elevational view thereof;

FIG. 5 is a left side elevational view thereof; the right side elevational view being a mirror image;

FIG. 6 is a top left front perspective view of the alternate embodiment of a chair back showing our new design; and,

FIG. 7 is a rear elevational view of the alternate embodiment. The front plan, top plan, left side elevational and right side elevational views would be as expected from FIGS. 2, 3 and 5. 

The ornamental design for a chair back, as shown and described. 